The present invention is directed to the field of snow removal. More particularly, the present invention is directed to a snowplow blade lift mechanism which combines a counterbalance system with an actuation system which permits variable downward pressure to be applied to the blade.
Traditionally, snowplow blades have been bulky and heavy to maintain contact with the road no matter what obstruction was encountered and to endure the stresses and strains of snow removal. These snowplow blades were mounted on an articulated linkage and raised and lowered via some type of actuator. The full weight of the snowplow blade would engage the ground each time the snowplow was used. For most applications, this resulted in excessive downward pressure producing excessive wear of the blade, as well as the road, over-working the drive components, and resulting in excessive fuel consumption. With the rising cost of fuel, this inefficient system is in need of an overhaul.
The present lifting mechanism is designed for use with snowplow blades made with high strength, light weight materials. The lighter weight blade can, then, be mounted on a smaller, more fuel efficient vehicle and can be manipulated by a more efficient, less costly actuator. The lifting mechanism of the present invention employs a counterbalance system which, in one preferred embodiment, employs a plurality of coil springs connected between a push frame upon which the snowplow blade is mounted and a mounting frame attached to frame of the vehicle. The force administered by the counterbalance springs is variable by reconfiguring adjustment means, which in one embodiment is a turnbuckle, associated with each counterbalancing spring.
One end of a double-acting actuator is pivotally connected to the push frame and the other end is connected to the mounting frame by means of a toggle link. In at least one position midway in the travel of the actuator, the counterbalance springs bear the total weight of the push frame and snowplow blade and the actuator can be disconnected from the toggle link, if necessary, e.g., for actuator replacement. Since only a fractional amount of the weight of the snowplow blade assembly needs to be moved, the actuator can be smaller and its operation more efficient. The actuator moves the snowplow blade between a first retracted travel position and a second extended plowing position. In the first fully retracted position, the inboard end of the toggle link engages a stop pin which prevents further counterclockwise rotation of the toggle link resisting bouncing movement of the snowplow blade during transit with the stiffness of the mounting frame.
Once the blade is engaged with the road surface, variable downward pressure can be exerted on the blade edge. The downward pressure is variable between extremes of less than the weight of the snowplow blade to significantly more than the weight of the blade. This is made possible by additional extension of the actuator after the blade is in contact with the road, extending heavy duty spring means and, effectively, transferring a portion of the vehicular weight to the blade edge. This can assist in breaking ice or hard packed snow when needed. The downward pressure can be reduced for normal conditions and additionally reduced for soft road surfaces such as gravel. The snowplow blade is additionally equipped with a break-over pivot connection and a break-over spring which biases the snowplow blade back against a stop block. Should the blade encounter an immovable obstruction, the blade (or some portion thereof) can pivot forward against the force of the spring while simultaneously rising against the force of the download spring to prevent damage to the blade and the actuator.
Various other features, advantages and characteristics of the present invention will become apparent to one of ordinary skill in the art after a reading of the following specification.